Reactive mesogens (RMs), mixtures or formulations comprising them, and polymers obtained thereof, can be used to make optical components, like compensation, retardation or polarisation films, or lenses. These optical components can be used in optical or electrooptical devices like LC displays. Usually the RMs or RM mixtures are polymerised through the process of in-situ polymerisation.
The manufacture of RM film products with high birefringence is of high importance for manufacturing optical components of modern display devices like LCDs. Increasing the birefringence of the RM whilst keeping them polymerisable and with good physical properties is possible, but requires to incorporate specific chemical groups, like for example tolane groups, into the compounds. These tolane groups are relatively reactive and are generally unsuited to light exposure, making them difficult to utilise in many optical applications due to yellowing or other degradation effects.
It is therefore an aim of the present invention to provide improved RMs and RM formulations, which do not have the drawbacks of materials known from prior art. In particular it is an aim to provide RMs and RM formulations that are suitable for preparing polymers by in situ UV photopolymerisation, have a high birefringence, and show high resistance against yellowing after being exposed to UV light. Other aims of the invention are immediately evident to the expert from the following description.
The inventors have of the present invention have found that these aims can be achieved by providing RMs and RM formulations as disclosed and claimed hereinafter.